For those that spend a lot of time paying attention to developments in firearms technology, and have done so for any length of time, it's always interesting when new cartridges come out. What is more interesting is when these new cartridges become run-away successes. Such is the case of the .300 AAC Blackout cartridge.
While an in-depth discussion of the history of the 300 BLK as it's known officially is splattered all over the web, there is at least one point that gets completely lost: what about 300 Whisper?
If you don't know, 300 Whisper is the brain child of JD Jones of SSK Industries fame, arguably one of the most prolific and interesting cartridge designers of late. JDJ (his initials, but also a common suffix to cartridges he's created) has necked up/down just about every cartridge in regular commerce, his cartridges cover everything from .20" caliber through .950" caliber.
With that kind of track record, why is there are 300 BLK?
To draw attention the relevant history of the 300 BLK, Freedom Group went on a buying spree not too long ago, buying Remington, Mossberg, Barnes, AAC, Para, Bushmaster, DPMS and a few dozen others. They are a manufacturing conglomerate the firearms industry barely recognizes outside military circles. Why exactly they put development dollars into developing a new cartridge I can only guess, but AAC being a principle part of the development and having suppressors as a principle product, the 300 BLK was a natural fit for such investment.
Freedom group did something interesting after spending all that money, they published standards for the cartridge and then proceeded to make arms and ammunition in quantities that made it affordable for everyone, in very stark contrast to the business practices of SSK Industries.
At this point, most commercial barrels that are chambered for the 300 BLK will also accept 300 Whisper, the reverse is likely not true, however, as 300 Whisper is a wildcat cartridge it has no official standing with SAAMI, and is not included in the "unsafe cartridge combinations list".
It will be interesting to see if there is any further development or standardization of 300 Whisper, but this is a key example of the fundamental tenets of business. That being: There are three ways to make money at manufacturing, you can make something cheaper than everyone else, you can make something better than everyone else, or you can make something no one else does. It seems under the circumstances Freedom Group has changed the paradigm somewhat, you can make something cheaper and better than someone else when everyone makes it!
Tuesday, April 10, 2012
Friday, April 6, 2012
Shotgun Recipes - Load Data
To people familiar with metallic cartridge reloading, any foray into loading shotgun can be a confusing experience. Most loading manuals endorse strict adherence to the recipe threatening dangerous and dire consequences will be the result of any variation. Yet they never explain why.
If you have ever wondered why, this post will attempt to explain the science of shotgun shells. But first, lets become familiar with the components that make up a shotgun shell. In comparison to most centerfire cartridges with shotgun shells the only component visible is the hull or shell casing, whereas a metallic cartridge you will see the bullet sticking out from the case. While this may seem confusing, there is a huge benefit, as many shotgun hulls are made of transparent plastic allowing the internal components to be viewed without the shell being cross sectioned. As is shown:
So an explanation of the components. From left to right, the brass colored section at the rear is called the base, which includes the extraction rim. The next visible component is the powder, the dark stuff viewable just in front of the base through the plastic body. Next is a concave cup that provides a gas seal, in front of that is the wadding, followed by the shot, and then the hull is crimped at the front to close it and keep the shot in. With this in mind, a discussion of each feature in descending order of importance.
Crimp
Shotshell crimps come in several varieties, the 6 and 8 point crimps are by far the most common these days, the difference in each is mostly determined by the preference of the manufacturer, cheap disposable single use shells most commonly have the 6 point crimp, and more durable reloadable hulls utilize the 8-point type. Two other types that have been common over the years are the over-shot card, which is most commonly used on buckshot loads. An example is shown here:
The other crimp, which is performed in a similar method to the over-shot card is that used on shotgun slugs. In this case the overshot card is simply omitted and the shell casing is roll crimped around the slug.
Roll crimping is performed using a roll crimping machine, or tool which rotates against the leading edge of the shell, forcing the rim to be rolled over, and will continue rolling the front down until it encounters the card or a slug. There are several sources for roll crimping tools. Ballistic Products manufactures a series of roll crimping tools for every common gauge of shotshell. The alternative is an antique roll crimping tool made by Ideal (now lyman), I couldn't find a convenient picture.
Crimp is one of the two most important features of any shotgun shell, because the type, length and geometry of the crimp determine the internal capacity of a closed shotgun shell. Folded multipoint crimps are the most restrictive in terms of internal volume and do not allow for much tolerance in terms of internal volume, a large shot, powder charge, and long wad selection will result in a recipe that will simply not stuff into the internal volume of the shotgun shell. This typically will result in the crimp bursting and all the shot coming out during handling. The inverse is also true, a reduction in shot, powder, or wad length will allow the crimp petals to cave inwards, again allowing the shot to spill out. In a certain sense, this is a good thing as it makes detecting rounds with an inadequate powder charge easy to pick out from properly loaded shells.
Roll type crimps (either for slugs, or for over-shot cards) are the most tolerant, but are only appropriate on shells that have been roll-crimped before, or new shells. Generally, the roll crimping process is not kind to plastic shells, and they are unlikely to survive more than one or two goes, paper shells tend to be more durable in this respect. That said, the advantage to a roll crimp is the internal capacity can vary more as the crimping process is not as rigid because the shell only needs to be able to fold back into itself to retain the components, it does not have to fold exactly closed.
Wad Selection
The modern plastic molded shotgun wad is arguably one of the most important developments for shotguns ever. To make a comparison to metallic rifle ammunition, the plastic wad is to the shotshell what boat-tail spitzer bullets are to modern rifle ammunition. Choosing the right wad is like choosing the right bullet if all other components are the same. With this in mind why is it so important? The picture shown here is a Claybuster Winchester Wad, a close copy of a WAA12 wad, one of the most common wads recognizable to anyone who has ever loaded Winchester AA hulls.
It is designed for a nominal load of 1 to 1-5/8oz of lead shot. For different loadings, the amount of powder or wad can be changed to make a good match for the internal volume of the shotgun shell you are loading it into. In Black Powder loadings, the WAA12R is a common wad, the buffer section (the part in the middle) is significantly shorter. In the WAA12SL, it is much longer.
The modern 1-piece wad has two functions that makes it so important, first, it compresses the gunpowder against the battery cup, and most importantly, it provides some elasticity to the internal volume of the shell. When the hull is being loaded, the wad will be compressed by some percentage, this has two functions, to tamp down the powder, and to make sure the shell is loaded to the correct over-all length. So finding a good match between your hull, the type of crimp you're using, your wad, shot charge, and powder charge is essential to making a good shell.
Powder Selection
Shotguns are very low pressure guns, where modern rifles may perform constantly at 60,000 PSI the shotgun would burst at those pressures, SAAMI lists a max pressure of 13,000PSI for 12ga shotguns. However, to complicate manners, the powder used in shotshells if not properly compressed with have difficulty reaching full ignition, resulting in a "blooper" as it's often called, based on the noise it makes.
The reason for the ignition problems is because shotgun bores are so large by comparison to their metallic cousins. The diameter of a 12ga barrel is .729" or thereabouts which is .5" greater in diameter than the venerable .30-06. This means that the volume of the 12ga will increase five times faster as the projectile travels down the barrel. So quick burning powders are a must. To keep pressures low, most shotguns use only 3-5 times the amount of powder used by pistols, where rifles may be 10 times (on a weight-weight basis) more powder.
Powders such as Hodgdon Clays, W231, bullseye, IMR700X are choice powders for loading shotgun shells. All of these powders tend to be very bulky, large flake powders, making them easy to ignite, and able to take up the necessary space at the base of the shotgun shell in addition to having relatively fast burn rates.
Hull Selection
The hull selection is quite critical in terms of internal volume, as the length of the hull will change where the crimp goes, however hulls are standard sizes (or very close to it) being at 2-1/2", 2-3/4", 3" and 3-1/2" each of these numbers represent the "open" length of the hull, or the length before crimping. While a 3" loaded round may fit into a 2-3/4" chamber, firing it would be very dangerous as the crimp would open up into the forcing cone of the chamber (think of this like the throat on a rifle) causing pressures to spike.
Hulls come in a wide variety of shapes, sizes, constructions, and internal volumes. So while hull selection is a critical factor for maintaining consistent and safe performance for a recipe, hull variation in a single brand/model is almost non-existent.
Primer Selection
I may be a bit cavalier, but in my years of loading shotshell, I have yet to notice many significant differences between shotgun primer types. They all seem to be about the same power, and same dimensions. While I tend to run minimum loads, I have never had problems switching between primer brands. But as a cautionary note, this is considered among the cardinal sins to adherents of the shotshell recipe cult. But it is worth noting that the #209 primer, no matter manufacturer should be exactly the same, as #209 is a primer standard that specifies both the size of the primer, the battery cup but also the amount of priming material and any other ignition characteristics of the primer.
Shot Selection
When it comes to recipe creation, the size of shot, the hole size in the bar that meters the shot, and the type of shot can greatly affect how the load will perform. The primary reason for this, is the smaller (the higher the number) the more densely the individual pellets can stack together in the shell. This is very easy to visualize when you try to stack a few pieces of buckshot into a shell, vs a few spoonfulls of #12.
As a consequence of these density variations, a load of #12 may be the volumetric equivalent of 1oz of #7.5, but may be 50% heavier, which could be a dangerous combination. The reverse is also true, 1oz of #12, could be equivalent to 3/4oz of #7.5, but the lack of inertia may lead to a blooper.
In this way, knowing your components, is a very critical factor when creating a shotgun recipe and tends to be one few people will mess with with any regularity.
As long as I'm on the topic of shot, there is more to load than simple wads full of shot, at least two manufacturers offer molds for casting your own slugs, lee and lyman are the largest, I am sure there are others out there. Lee however takes the most interesting approach. The Lee slug, is equal in length, to the length of a similar weight of #7.5 shot (approximately). Therefore if you are set up to load a 1oz #7.5 load, removing the shot bottle, and instead inserting a slug after the wad has been inserted and precompressed, and before crimping you can load your own shotgun slugs for pennies compared to what they cost at the gun shop.
Shotgun cartridges are much more complex than their metallic counterparts, they have more components and the way they are assembled seems to be a floating quantity. For most people, sticking to the recipe is the safest, that said, at least you now know why.
If you have ever wondered why, this post will attempt to explain the science of shotgun shells. But first, lets become familiar with the components that make up a shotgun shell. In comparison to most centerfire cartridges with shotgun shells the only component visible is the hull or shell casing, whereas a metallic cartridge you will see the bullet sticking out from the case. While this may seem confusing, there is a huge benefit, as many shotgun hulls are made of transparent plastic allowing the internal components to be viewed without the shell being cross sectioned. As is shown:
So an explanation of the components. From left to right, the brass colored section at the rear is called the base, which includes the extraction rim. The next visible component is the powder, the dark stuff viewable just in front of the base through the plastic body. Next is a concave cup that provides a gas seal, in front of that is the wadding, followed by the shot, and then the hull is crimped at the front to close it and keep the shot in. With this in mind, a discussion of each feature in descending order of importance.
Crimp
Shotshell crimps come in several varieties, the 6 and 8 point crimps are by far the most common these days, the difference in each is mostly determined by the preference of the manufacturer, cheap disposable single use shells most commonly have the 6 point crimp, and more durable reloadable hulls utilize the 8-point type. Two other types that have been common over the years are the over-shot card, which is most commonly used on buckshot loads. An example is shown here:
The other crimp, which is performed in a similar method to the over-shot card is that used on shotgun slugs. In this case the overshot card is simply omitted and the shell casing is roll crimped around the slug.
Roll crimping is performed using a roll crimping machine, or tool which rotates against the leading edge of the shell, forcing the rim to be rolled over, and will continue rolling the front down until it encounters the card or a slug. There are several sources for roll crimping tools. Ballistic Products manufactures a series of roll crimping tools for every common gauge of shotshell. The alternative is an antique roll crimping tool made by Ideal (now lyman), I couldn't find a convenient picture.
Crimp is one of the two most important features of any shotgun shell, because the type, length and geometry of the crimp determine the internal capacity of a closed shotgun shell. Folded multipoint crimps are the most restrictive in terms of internal volume and do not allow for much tolerance in terms of internal volume, a large shot, powder charge, and long wad selection will result in a recipe that will simply not stuff into the internal volume of the shotgun shell. This typically will result in the crimp bursting and all the shot coming out during handling. The inverse is also true, a reduction in shot, powder, or wad length will allow the crimp petals to cave inwards, again allowing the shot to spill out. In a certain sense, this is a good thing as it makes detecting rounds with an inadequate powder charge easy to pick out from properly loaded shells.
Roll type crimps (either for slugs, or for over-shot cards) are the most tolerant, but are only appropriate on shells that have been roll-crimped before, or new shells. Generally, the roll crimping process is not kind to plastic shells, and they are unlikely to survive more than one or two goes, paper shells tend to be more durable in this respect. That said, the advantage to a roll crimp is the internal capacity can vary more as the crimping process is not as rigid because the shell only needs to be able to fold back into itself to retain the components, it does not have to fold exactly closed.
Wad Selection
It is designed for a nominal load of 1 to 1-5/8oz of lead shot. For different loadings, the amount of powder or wad can be changed to make a good match for the internal volume of the shotgun shell you are loading it into. In Black Powder loadings, the WAA12R is a common wad, the buffer section (the part in the middle) is significantly shorter. In the WAA12SL, it is much longer.
The modern 1-piece wad has two functions that makes it so important, first, it compresses the gunpowder against the battery cup, and most importantly, it provides some elasticity to the internal volume of the shell. When the hull is being loaded, the wad will be compressed by some percentage, this has two functions, to tamp down the powder, and to make sure the shell is loaded to the correct over-all length. So finding a good match between your hull, the type of crimp you're using, your wad, shot charge, and powder charge is essential to making a good shell.
Powder Selection
Shotguns are very low pressure guns, where modern rifles may perform constantly at 60,000 PSI the shotgun would burst at those pressures, SAAMI lists a max pressure of 13,000PSI for 12ga shotguns. However, to complicate manners, the powder used in shotshells if not properly compressed with have difficulty reaching full ignition, resulting in a "blooper" as it's often called, based on the noise it makes.
The reason for the ignition problems is because shotgun bores are so large by comparison to their metallic cousins. The diameter of a 12ga barrel is .729" or thereabouts which is .5" greater in diameter than the venerable .30-06. This means that the volume of the 12ga will increase five times faster as the projectile travels down the barrel. So quick burning powders are a must. To keep pressures low, most shotguns use only 3-5 times the amount of powder used by pistols, where rifles may be 10 times (on a weight-weight basis) more powder.
Powders such as Hodgdon Clays, W231, bullseye, IMR700X are choice powders for loading shotgun shells. All of these powders tend to be very bulky, large flake powders, making them easy to ignite, and able to take up the necessary space at the base of the shotgun shell in addition to having relatively fast burn rates.
Hull Selection
The hull selection is quite critical in terms of internal volume, as the length of the hull will change where the crimp goes, however hulls are standard sizes (or very close to it) being at 2-1/2", 2-3/4", 3" and 3-1/2" each of these numbers represent the "open" length of the hull, or the length before crimping. While a 3" loaded round may fit into a 2-3/4" chamber, firing it would be very dangerous as the crimp would open up into the forcing cone of the chamber (think of this like the throat on a rifle) causing pressures to spike.
Hulls come in a wide variety of shapes, sizes, constructions, and internal volumes. So while hull selection is a critical factor for maintaining consistent and safe performance for a recipe, hull variation in a single brand/model is almost non-existent.
Primer Selection
I may be a bit cavalier, but in my years of loading shotshell, I have yet to notice many significant differences between shotgun primer types. They all seem to be about the same power, and same dimensions. While I tend to run minimum loads, I have never had problems switching between primer brands. But as a cautionary note, this is considered among the cardinal sins to adherents of the shotshell recipe cult. But it is worth noting that the #209 primer, no matter manufacturer should be exactly the same, as #209 is a primer standard that specifies both the size of the primer, the battery cup but also the amount of priming material and any other ignition characteristics of the primer.
Shot Selection
When it comes to recipe creation, the size of shot, the hole size in the bar that meters the shot, and the type of shot can greatly affect how the load will perform. The primary reason for this, is the smaller (the higher the number) the more densely the individual pellets can stack together in the shell. This is very easy to visualize when you try to stack a few pieces of buckshot into a shell, vs a few spoonfulls of #12.
As a consequence of these density variations, a load of #12 may be the volumetric equivalent of 1oz of #7.5, but may be 50% heavier, which could be a dangerous combination. The reverse is also true, 1oz of #12, could be equivalent to 3/4oz of #7.5, but the lack of inertia may lead to a blooper.
In this way, knowing your components, is a very critical factor when creating a shotgun recipe and tends to be one few people will mess with with any regularity.
As long as I'm on the topic of shot, there is more to load than simple wads full of shot, at least two manufacturers offer molds for casting your own slugs, lee and lyman are the largest, I am sure there are others out there. Lee however takes the most interesting approach. The Lee slug, is equal in length, to the length of a similar weight of #7.5 shot (approximately). Therefore if you are set up to load a 1oz #7.5 load, removing the shot bottle, and instead inserting a slug after the wad has been inserted and precompressed, and before crimping you can load your own shotgun slugs for pennies compared to what they cost at the gun shop.
Shotgun cartridges are much more complex than their metallic counterparts, they have more components and the way they are assembled seems to be a floating quantity. For most people, sticking to the recipe is the safest, that said, at least you now know why.
Wednesday, April 4, 2012
Load Development (Part 5)
Thanks for sticking with me, this is going to be a monster post, not so much in it's length but in the amount of detail I'm about to get into.
Data Analysis - Making sense of it all
Up to now all of these steps have been like making a pie, all of the ingredients have gone into the bowl, been mixed, rolled, and stuffed with fruit, if the last installment was like tasting the pie, this section is going to be about how we can make that pie better.
So by now you probably have a bunch of shell casings that are all dirty and waiting for their next reload, maybe you have a chronograph with dead batteries, a sunburn and are in dire need of a shower. However, you also have a very valuable piece of paper that contains all of the data you took from the last trip to the range.
Rather than exhaustively going through every single load, lets make a spreadsheet we can put our data into. Personally, I tend to use Microsoft Excel, because that's what's on my computer, and that's what I've been using for years. Not to create a debate about which spreadsheet is best, any of them will work provided it has functions that SUM, AVG, and Standard Deviation.
Unfortunately, I couldn't find my old test data from when I developed my .223 69gr load, and a number of the other development projects I've done were done with bulk powders, and are proprietary to some of my former employers. But here is some test data from some .308 Loadings I did some time ago, you're welcome to use these loads, however I assume no liability, or make any assumptions about their usefulness for anything. That said:
Barnes 30842 FC IMR3031 41.5 WLR 2.795
2803 2772 2787 2774 2787
Barnes 30842 FC IMR3031 41.5 Fed215 2.795
2771 2773 2796 2763 2731
Sierra 2200 FC Varget 42.0 WLR 2.750
2481 2515 2469 2491 2501 2500 2484 2490 2491 2503
Hornady 190gr HPBT FC IMR3031 38.5 WLR 2.795
2420 2428 2463 2429 2416 2441 2428 2439 2445 2440
As you can see, each of these loads varied, and I kept track of all the components used, the case, powder, bullet type (by manufacturer number), primer, and the OAL.
That said, lets crunch some numbers:
Avg Velocity Standard Deviation
Load 1 2784.6 12.46
Load 2 2766.8 23.48
Load 3 2491.4 12.96
Load 4 2431.2 13.67
Now for those of you who are not too familiar with statistics, and either didn't read, or didn't care to understand exactly what Standard Deviation is, this means that there is a statistical probability that about 75% of the rounds fired will be within 1 standard deviation of the average velocity in column 2.
Generally, the accuracy of ammunition is not an important factor, this is why firearms have adjustable sights, what is important is consistency, so the more identical one round of ammunition is to the next, the higher the probability of you putting bullet after bullet into the bullseye.
In general again, I am willing to tolerate a maximum SD of 20FPS in any rifle ammunition I am producing either for my handloads, or that I will be producing as a factory loading. Ideally, I like all SDs to be under 10FPS, but this is a very difficult goal with rifle ammunition. The reason it is so difficult is the extreme conditions rifle ammunition operates under, every little change will be magnified exponentially. Also, every round doesn't have to be perfect, it just has to be close enough to the last round that no one notices.
So of the loads tested, and the data presented, which loads do you think I decided to keep, and which did I decide to discard?
If you notice, the first two loads are the same charge of powder, same bullet, same case, same everything, just different primer. Interestingly, the winchester primer was both more consistent, and attained a higher muzzle velocity than the federal 215 (large rifle mag) primers.
With this in mind, if you said drop Load 2, you're right! For a number of reasons I don't like Federal primers, usually because they are excessively soft, and thus tend to have problems with consistent seating depth. It seems now there's just another reason I don't have to bother keeping them in stock.
Since I have not really touched on it yet, group size is another one of those important things you need to keep in mind. Unfortunately, I couldn't find any of my old targets from this day of testing, seeing as how it was several years ago, this is not surprising.
So with that in mind, lets talk about what is considered "good" in terms of group size.
Military Standards for small arms ammunition usually specifies a maximum group size with a radius of 2 minutes of angle, (2MOA) which is about a 4" circle at 100 yards, it's worth noting, that in the civilian world, the MOA measurement of a group is a diameter, not a radius. Therefore, a 2MOA radius group is actually a 4MOA group in the civilian world.
For any ammo I consider this an absolute bare minimum accuracy standard, and would consider any experiment that produced results that only met this standard to be a dismal failure. For regular FMJ-BT "blasting" ammo that I use for regular every day shooting, I consider a 2MOA radius to be good enough for production ammunition, 1.5MOA ammo to be good enough to be considered match ammunition, and any ammo that shoots better than this an unbridled success. In general, 1MOA is a tough goal to get to with production ammunition, but it is attainable with handloads. Additionally, a 1MOA envelope the capabilities of the gun start to matter just as much as the ammunition.
Creating consistent ammunition can be quite a chore given all of the choices out there for bullet, powder, primer and case, the magic to getting those numbers where you want them can be quite difficult, but experience in selecting components can help quite a bit.
Data Analysis - Making sense of it all
Up to now all of these steps have been like making a pie, all of the ingredients have gone into the bowl, been mixed, rolled, and stuffed with fruit, if the last installment was like tasting the pie, this section is going to be about how we can make that pie better.
So by now you probably have a bunch of shell casings that are all dirty and waiting for their next reload, maybe you have a chronograph with dead batteries, a sunburn and are in dire need of a shower. However, you also have a very valuable piece of paper that contains all of the data you took from the last trip to the range.
Rather than exhaustively going through every single load, lets make a spreadsheet we can put our data into. Personally, I tend to use Microsoft Excel, because that's what's on my computer, and that's what I've been using for years. Not to create a debate about which spreadsheet is best, any of them will work provided it has functions that SUM, AVG, and Standard Deviation.
Unfortunately, I couldn't find my old test data from when I developed my .223 69gr load, and a number of the other development projects I've done were done with bulk powders, and are proprietary to some of my former employers. But here is some test data from some .308 Loadings I did some time ago, you're welcome to use these loads, however I assume no liability, or make any assumptions about their usefulness for anything. That said:
Barnes 30842 FC IMR3031 41.5 WLR 2.795
2803 2772 2787 2774 2787
Barnes 30842 FC IMR3031 41.5 Fed215 2.795
2771 2773 2796 2763 2731
Sierra 2200 FC Varget 42.0 WLR 2.750
2481 2515 2469 2491 2501 2500 2484 2490 2491 2503
Hornady 190gr HPBT FC IMR3031 38.5 WLR 2.795
2420 2428 2463 2429 2416 2441 2428 2439 2445 2440
As you can see, each of these loads varied, and I kept track of all the components used, the case, powder, bullet type (by manufacturer number), primer, and the OAL.
That said, lets crunch some numbers:
Avg Velocity Standard Deviation
Load 1 2784.6 12.46
Load 2 2766.8 23.48
Load 3 2491.4 12.96
Load 4 2431.2 13.67
Now for those of you who are not too familiar with statistics, and either didn't read, or didn't care to understand exactly what Standard Deviation is, this means that there is a statistical probability that about 75% of the rounds fired will be within 1 standard deviation of the average velocity in column 2.
Generally, the accuracy of ammunition is not an important factor, this is why firearms have adjustable sights, what is important is consistency, so the more identical one round of ammunition is to the next, the higher the probability of you putting bullet after bullet into the bullseye.
In general again, I am willing to tolerate a maximum SD of 20FPS in any rifle ammunition I am producing either for my handloads, or that I will be producing as a factory loading. Ideally, I like all SDs to be under 10FPS, but this is a very difficult goal with rifle ammunition. The reason it is so difficult is the extreme conditions rifle ammunition operates under, every little change will be magnified exponentially. Also, every round doesn't have to be perfect, it just has to be close enough to the last round that no one notices.
So of the loads tested, and the data presented, which loads do you think I decided to keep, and which did I decide to discard?
If you notice, the first two loads are the same charge of powder, same bullet, same case, same everything, just different primer. Interestingly, the winchester primer was both more consistent, and attained a higher muzzle velocity than the federal 215 (large rifle mag) primers.
With this in mind, if you said drop Load 2, you're right! For a number of reasons I don't like Federal primers, usually because they are excessively soft, and thus tend to have problems with consistent seating depth. It seems now there's just another reason I don't have to bother keeping them in stock.
Since I have not really touched on it yet, group size is another one of those important things you need to keep in mind. Unfortunately, I couldn't find any of my old targets from this day of testing, seeing as how it was several years ago, this is not surprising.
So with that in mind, lets talk about what is considered "good" in terms of group size.
Military Standards for small arms ammunition usually specifies a maximum group size with a radius of 2 minutes of angle, (2MOA) which is about a 4" circle at 100 yards, it's worth noting, that in the civilian world, the MOA measurement of a group is a diameter, not a radius. Therefore, a 2MOA radius group is actually a 4MOA group in the civilian world.
For any ammo I consider this an absolute bare minimum accuracy standard, and would consider any experiment that produced results that only met this standard to be a dismal failure. For regular FMJ-BT "blasting" ammo that I use for regular every day shooting, I consider a 2MOA radius to be good enough for production ammunition, 1.5MOA ammo to be good enough to be considered match ammunition, and any ammo that shoots better than this an unbridled success. In general, 1MOA is a tough goal to get to with production ammunition, but it is attainable with handloads. Additionally, a 1MOA envelope the capabilities of the gun start to matter just as much as the ammunition.
Creating consistent ammunition can be quite a chore given all of the choices out there for bullet, powder, primer and case, the magic to getting those numbers where you want them can be quite difficult, but experience in selecting components can help quite a bit.
Monday, April 2, 2012
Load Development (Part 4)
Hopefully everyone is still reading this, as I got busy for a few days and didn't have time to finish up this article (One more post after this one, I promise!). Either way here's another installment.
Gathering Data - Time to hit the range!
So here is the fun, and yet at times tedious part of this processes. Aside from interpreting data (the next section) this is where you're most likely to go wrong, so attention to detail is critically important in this phase.
If you're getting ready to go to the range to test out some new loads, here's a quick checklist:
* The gun
* The ammo
* Calibrated targets or Overlays
* Chronograph (DON'T FORGET SPARE BATTERIES!!!!!)
- All of the other bits and bobs that go to the chrono, make sure you have a tripod to put it on, some sandbags to weigh it down with so it doesn't blow over, wires, spare wires, extra sky screens etc.
* Pad and paper
* Something to write with
If you are on your way to the range and you forgot any of these things, you may as well turn around and go home now, otherwise you will not collect any useful data.
Hopefully you remembered everything, bought it on the way, or were lucky enough to borrow something you forgot when you arrived. So lets go over some basics of equipment set up.
Set up your calibrated targets at a designated range (and the range for which they are calibrated for), now hopefully you have long line-breaks, as you will now need to set up the skyscreen assembly for your chronograph. Having a friend here can help quite a bit.
Place your skyscreens from 5-20' from the bench, 5' is ok for pistols, 20' is better for rifles, otherwise the muzzle blast can disassemble your sky screens just as easily as a bullet strike will. Once you have the distance right, having a friend who can stand behind your bench, directing you to move left-right-up-down, angle up or angle down and line up the skyscreen is definitely worth buying them lunch for showing up. In a pinch, most of the other people at the range will also be happy to help you with this operation, however, sometimes their skill at direction is greatly lacking.
Once you have access to your bench (line's now hot!), you should first fire some known ammo through the chronograph to make sure it's measuring properly. Measurements that are outside the norm, measurements that are missed, or measurements taken when you are not shooting can be an indication of bad placement of the chronograph, or of environmental interference (wind and florescent lights are the two biggest offenders except perhaps for no lights).
After testing your equipment the fun stuff begins. Make notes of which load you are testing, you can number them, or simply write down the details of each cartridge. i.e. Load 1 or 24.3grs varget...
When you fire the first round in a string, be sure to catch the first fired round, inspect the case, look at the primer, and look for signs of high pressure, if any is found you may not want to shoot the rest of the string, or shoot loads of more powder. Keep notes of any signs you see on the cartridge case, whether there are signs of high (even if not excessive pressure), also make notes about the ambient conditions, most cartridges will generate higher pressures with hotter ambient temperatures.
At the end of each fired string, switch to using a different bullseye on the target, and measure group size wither with overlays, or using calibrated targets. Make notes of which loads have a smaller group size.
As I said earlier, load development can be a very time consuming process, and is easier to perform with a test range at hand, this makes gathering data much faster, requires loading fewer rounds, and there is no waiting for line breaks.
By now, you should hopefully have taken some good data. The next article is going to be all about data analysis.
Gathering Data - Time to hit the range!
So here is the fun, and yet at times tedious part of this processes. Aside from interpreting data (the next section) this is where you're most likely to go wrong, so attention to detail is critically important in this phase.
If you're getting ready to go to the range to test out some new loads, here's a quick checklist:
* The gun
* The ammo
* Calibrated targets or Overlays
* Chronograph (DON'T FORGET SPARE BATTERIES!!!!!)
- All of the other bits and bobs that go to the chrono, make sure you have a tripod to put it on, some sandbags to weigh it down with so it doesn't blow over, wires, spare wires, extra sky screens etc.
* Pad and paper
* Something to write with
If you are on your way to the range and you forgot any of these things, you may as well turn around and go home now, otherwise you will not collect any useful data.
Hopefully you remembered everything, bought it on the way, or were lucky enough to borrow something you forgot when you arrived. So lets go over some basics of equipment set up.
Set up your calibrated targets at a designated range (and the range for which they are calibrated for), now hopefully you have long line-breaks, as you will now need to set up the skyscreen assembly for your chronograph. Having a friend here can help quite a bit.
Place your skyscreens from 5-20' from the bench, 5' is ok for pistols, 20' is better for rifles, otherwise the muzzle blast can disassemble your sky screens just as easily as a bullet strike will. Once you have the distance right, having a friend who can stand behind your bench, directing you to move left-right-up-down, angle up or angle down and line up the skyscreen is definitely worth buying them lunch for showing up. In a pinch, most of the other people at the range will also be happy to help you with this operation, however, sometimes their skill at direction is greatly lacking.
Once you have access to your bench (line's now hot!), you should first fire some known ammo through the chronograph to make sure it's measuring properly. Measurements that are outside the norm, measurements that are missed, or measurements taken when you are not shooting can be an indication of bad placement of the chronograph, or of environmental interference (wind and florescent lights are the two biggest offenders except perhaps for no lights).
After testing your equipment the fun stuff begins. Make notes of which load you are testing, you can number them, or simply write down the details of each cartridge. i.e. Load 1 or 24.3grs varget...
When you fire the first round in a string, be sure to catch the first fired round, inspect the case, look at the primer, and look for signs of high pressure, if any is found you may not want to shoot the rest of the string, or shoot loads of more powder. Keep notes of any signs you see on the cartridge case, whether there are signs of high (even if not excessive pressure), also make notes about the ambient conditions, most cartridges will generate higher pressures with hotter ambient temperatures.
At the end of each fired string, switch to using a different bullseye on the target, and measure group size wither with overlays, or using calibrated targets. Make notes of which loads have a smaller group size.
As I said earlier, load development can be a very time consuming process, and is easier to perform with a test range at hand, this makes gathering data much faster, requires loading fewer rounds, and there is no waiting for line breaks.
By now, you should hopefully have taken some good data. The next article is going to be all about data analysis.
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